Metal cutting tool



Patented July 28, 1942 UNITED STATES PATENT OFFICE METAL CUTTING TOOLRudolf W. Andreasson, Detroit, Mich.

Application March 28, 1942, Serial No. 436,687

2 Claims.

This invention relates to metal cutting tools such as drills and thelike and in particular to a method and means for providing a fluidpassage therethrough.

This application is a continuation-in-part of the co-pending applicationfor patent of Rudolf W. Andreasson entitled Method of manufacturingmetal cutting tools, Serial No. 412,779 filed September 29, 1941.

In gun drills and twist drills it is customary to provide a fluidpassage longitudinally thereof through which cutting compound, lubricantand coolant is forced under pressure to the working .end of the cuttingtip. In other types of metal cutting tools fluid passages are providedfor like purposes. Although the invention may be applied to varioustypes of metal cutting tools having fluid passages therethrough,inasmuch as the invention is most applicable to gun drills and twistdrills, it will be described with particular reference thereto.

In long gun drills and twist drills and particu-. larly in smalldiameter gun drills and twist drills, it is extremely diflicult andsometimes impossible to provide long longitudinal bores therethroughbecause the limited diameter of the stock available limits the diameterof the hole to be bored. Accordingly, long gun drills are ofttimesconstructed of a solid shank drilled axially to com-- municate with ahollow shaft brazed or welded thereto, and onto the end of said shaft isbrazed or welded a cutting tip axially bored to communicate with thehollow shaft, thus providing a continuous fluid passage from the top ofthe shank to the extreme end of the cutting tip. I-Ieretofore, no fluidpassage has been possible axially through twist drills of, smalldiameters and long lengths because of lack of stock through which todrill or because of the impracticability of drilling long small diameterholes.

With the foregoing in view, the primary object of the invention is toprovide a gun drill, twist drill or the like having an inexpensive andreadily formed fluid passage from the top of the shank to the cuttingtip thereof.

Another object of the invention is to provide an inexpensive and facilemethod for forming a fluid passage from the upper end of the shank tothe cutting tip of long and small diameter gun and twist drills withoutadversely affecting the hardness or temper of the cutting edges thereof.

Another object of the invention is to provide a simple, effective andinexpensive method for providing a long or tortuous fluid passagethrough metal cutting tools and the like to the cutting tip or facethereof.

Other objects of the invention will become apparent by reference to thefollowing detailed description taken in connection with the accompanyingdrawing, in which:

Fig. 1 is a side elevational view of a gun drill manufactured inaccordance with the invention.

Fig. 2 is a side elevational View of the gun drill disclosed in Fig. 1taken on the line 22 of Fig. 1.

Fig. 3 is an enlarged fragmentary longitudinal sectional view taken onthe line 33 of Fig. 1 showing the gun drill bored, milled and preparedfor brazing.

Fig. 4 is a greatly enlarged cross sectional view of the gun drilldisclosed in Figs. 1 and 2 showing the slot milled longitudinallytherein providing a continuous fluid passage and continuous bridge rodseats.

Fig. 5 is a greatly enlarged cross sectional View similar to Fig. 4showing the fluid passage slot and bridge rod seats coated in accordancewith the invention.

Fig. 6 is a greatly enlarged cross sectional view similar to Fig. 5taken on the line 6-6 of Fig. 3 showing the gun drill having a bridgerod seated on the seats provided adjacent the top of the milled fluidpassage slot therein ready for brazmg.

Fig. 7 is a greatly enlarged cross sectional view of the gun drillsimilar to Fig. 6 except the bridge rod is securely brazed and the fluidpassage permanently formed.

Fig. 8 is a greatly enlarged cross sectional view of the completed gundrill and cutting tip taken on the lines 88 of Fig. 1.

Fig. 9 is a side elevational View of a twist drill manufactured inaccordance with the invention.

Fig. 10 is a side elevational view of the twist drill disclosed in Fig.9 taken on the line |0-l0 of Fig. 9.

Fig. 11 is a greatly enlarged cross sectional view of the twist drilldisclosed in Figs. 9 and 10 taken on the line l|--ll of Fig. 9.

Referring now to the drawing wherein like numerals refer to like andcorresponding parts throughout the several views, the illustrativeembodiment of the invention disclosed in Figs. 1-8 inclusive comprises agun drill generally designated by the numeral 20 having a tapered shank2|, a solid V-shaped shaft 22 preferably integral with the said taperedshank 2|, and a hardened steel V-shaped cutting tip 23 butt welded tothe bottom of the said shaft 22 as indicated by the reference numeral 24in Figs. 1 and 2.

The tapered shank 2| of the gun drill 20 is preferably provided with anaxial bore 25 and the said shaft 22 and cutting tip 23 have alongitudinal slot 28 milled therein. A diagonal bore 21 provides apassage communicating between the axial bore 25 in the tapered shank 2!and the upper end of the slot 26 formed in the said shaft 22. The saidslot 26 is preferably U- shaped in cross section at its base andV-shaped in cross section at the upper portion with a seat 263 formed ateach side thereof as best indicated in Fig. 4 to receive a relativelyfiat bridge rod or wire 28. The bridge rod or wire 23 held by anysuitable manner in the slot 2'6 on the seats 25%; for example, by tackbrazing as indicated by the numeral 29 in Fig. 3, or by the use ofclamps or jigs, not shown.

The bridge rod 28 is secured in its seated position in the top of theslot 26 by brazing on top and on each side thereof as indicated by thenumeral 36 in Fig. 7, the said bridge rod 28 serving as a form toprevent the filling. of brass or the like from running down into thebottom of the. said slot 52% The foregoing construction provides acontinuous fluid passage from the top of the shank 2! of the gun drill29 to the working end of the cutting tip 23 thereof. The protrudingportion and surplus filler or brazing material 39 is removed by suchmeans as cutting or grinding after which the surface of the drill ispreferably polished.

Prior to placing the bridge rod or wire 28 in the slot 23 on the seats269 as indicated in Fig. 6, the said slot 26 is lined or painted withacompound 3l such as carbon and graphite, or, carbonand a silica binder,or the like as indicated in Fig. which serves as a form and filler belowany interstices that may occur between the bridge rod or wire 28 and theside Walls of the said slot 2 5, thus preventing any brazing material 36from running down into the bottom of the said slot 25 and blocking thecomplete fluid passage 32. Any compound 3| which adheres to the faces 33of the slot 26 or which becomes smeared onto the exposed upper portionand sides of the bridge rod or wire 28 is preferably buffed. scraped orwiped off therefrom before brazing.

Obviously, a wide range of shapes of the slot 26 and the bridge rod orwire 28' can be" used in practicing the invention; By employing thecoating compound S-l, the minute interstices between the bridge rod orwire 28 and the seats Kill-are efiectively closed. The coating'compoundSi is preferably a carbon-graphite composition which adheres to thewalls of the slot 26 and, in addition to filling the minute intersticesbetween the bridge rod or wire 28 and the seats 260, serves to preventany brazing material which might possibly leak into the-slot 26 duringbrazing from adhering thereto. After brazing, the carbon-graphite lining3| is blown or washed out together with any brazing material that mayhave run through into the completed fluid passage 32, which brazingmaterial, because of the presence of the carbon-graphite lining 3|,takes the form of little globules easily washed or blown out from thesaid ccmpletedfiuidpassage 32.

It will be noted that the bridge rod or wire 28 actually seats on theside walls ofthe slot 25, and that chips and the like cannot possiblyforce the bridge rod or wire 28 to the bottom of the slot 2% during use.

Figs. 9 to 11 inclusiveshow a twist drill 40- having a tapered shank 4]provided with tortuous fluid passages 42 extending from the cutting tip43 up the outside face of the twisted shaft 44 and communicating with anaxial bore 45 in the tapered shank 4| by means of a diagonal bore 46.Each of the said tortuous fluid passages 42 comprises a milled slot 41having the top thereof flared to form seats 48 onto which a bridge rodor wire 49 is seated and brazed in place by suitable brazing 53 in alike and similar manner to the method hereinbefore described inconnection with the gun drill shown in Figs. 1 to 8 inclusive; thetortuous fluid passages 42 being preferably lined with a carbon-graphitecoating compound prior to positioning the bridge rod or wire 49thereover and brazing, which coating compound is subsequently removed byforcing air or water through the said fluid passages.

By employing a bridge rod or wire 28 and 49 in the top of the slots 26and 41 respectively much less brazing material 29 and 50 is requiredthan if the top of the slot 26 and 41 were completely filled withbrazing material, thus cutting down the temperature to which the metalof the cutting tool is raised by the process of brazing thereby beingassured that no deleterious annealing of the cutting edges of the metalcutting tool will occur during the providing of a longitudinal-fiuidpassage therethrough in the manner hereinbefore described.

Although but two embodiments of the invention and a single method ofpracticing the invention have been disclosed and described in I detail,it is obvious that many changes may be made in the size, shape,arrangement and detailof the elementsof the invention and in the methodof practicing the same without departing from the spirit of theinvention as defined by the appendedclaims.

I claim:

1. The method of providing a fluid supply passage in cutting toolscomprising the steps of milling a slot insaid tool wider at the surfaceof thetool than at the base of said slot and simultaneously formingcontinuous seats in the side walls of the said slot, disposing arelatively flat bridge rod wider than the narrowest portion of said slotin the top ofsaid slot supported laterally on said seats, coating thesaid slot prior to seating said bridge rod on said seats'withanonhardening material serving as high temperature sealing means forinterstices between said bridge rod and the sides of saidslot', holdingsaid bridge rod in said seated position, removing said coating materialfrom said bridge rod and the sides of said slot above said seats;brazing said bridge rod to said tool-while seated on said'seats byfilling the groove on each side of said bridge rod between said bridgerod and said tool and coveringsaid bridge rod-withthe material employed,removing the portion of said brazing material disposed above thes'urface-of-said tool, and removing. said coating material from withinthe completed: fluid supply passage.

2. The method of providing a fluid supply passage in cuttingtools-comprising the steps of milling a slot in said tool wider at thesurface of the tool than at the base of said slot and simultaneouslyforming continuous seats in the side walls of the said slot, disposing arelatively flat bridge rod wider than the narrowest portion of said slotin' the top of said slot supported laterally on said seats, coating thesaid'slot'prior to seating said'bridge' rod on said seats with acarbongraphite composition serving as sealing means forintersticesbetween saidbridge rod and'the bridge rod with the materialemployed, removing the portion of said brazing material disposed abovethe surface of said tool, and removing said coating material from withinthe completed fluid 5 supply passage.

RUDOLF W. ANDREASSON.

